package cn.duxiaod.demo.lock;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.AbstractQueuedSynchronizer;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;

public class ExclusiveDemo implements Lock {

    private static class Sync extends AbstractQueuedSynchronizer{
        // 是否处于独占状态
        @Override
        protected boolean isHeldExclusively() {
            return this.getState() == 1;
        }
        // 当状态为0时，获取锁
        @Override
        protected boolean tryAcquire(int arg) {
            if(compareAndSetState(0,1)){
                setExclusiveOwnerThread(Thread.currentThread());
                return true;
            }
            return false;
        }
        // 释放锁，将状态设置为0
        @Override
        protected boolean tryRelease(int arg) {
            if(getState() == 0) throw new IllegalMonitorStateException();
            setExclusiveOwnerThread(null);
            setState(0);
            return true;
        }
        // 返回一个Condition,没给Condition都包含了一个Condition队列
        Condition newCondition() {
            return new ConditionObject();
        }
    }

    private final Sync sync = new Sync();

    @Override
    public void lock() {
        sync.acquire(1);
    }

    @Override
    public void lockInterruptibly() throws InterruptedException {
        sync.acquireInterruptibly(1);
    }

    @Override
    public boolean tryLock() {
        return sync.tryAcquire(1);
    }

    @Override
    public boolean tryLock(long time, TimeUnit unit) throws InterruptedException {
        return sync.tryAcquireNanos(1,unit.toNanos(time));
    }

    @Override
    public void unlock() {
        sync.release(0);
    }

    @Override
    public Condition newCondition() {
        return sync.newCondition();
    }
}
